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Commit 571d76ac authored by Chris Metcalf's avatar Chris Metcalf
Browse files

arch/tile: support signal "exception-trace" hook 



This change adds support for /proc/sys/debug/exception-trace to tile.
Like x86 and sparc, by default it is set to "1", generating a one-line
printk whenever a user process crashes.  By setting it to "2", we get
a much more complete userspace diagnostic at crash time, including
a user-space backtrace, register dump, and memory dump around the
address of the crash.

Some vestiges of the Tilera-internal version of this support are
removed with this patch (the show_crashinfo variable and the
arch_coredump_signal function).  We retain a "crashinfo" boot parameter
which allows you to set the boot-time value of exception-trace.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent 8aaf1dda

arch/tile/include/asm/processor.h

+0 −7
Original line number Diff line number Diff line
@@ -257,10 +257,6 @@ static inline void cpu_relax(void) 
	barrier();

}



struct siginfo;

extern void arch_coredump_signal(struct siginfo *, struct pt_regs *);

#define arch_coredump_signal arch_coredump_signal



/* Info on this processor (see fs/proc/cpuinfo.c) */

struct seq_operations;

extern const struct seq_operations cpuinfo_op;
@@ -271,9 +267,6 @@ extern char chip_model[64]; 
/* Data on which physical memory controller corresponds to which NUMA node. */

extern int node_controller[];



/* Do we dump information to the console when a user application crashes? */

extern int show_crashinfo;



#if CHIP_HAS_CBOX_HOME_MAP()

/* Does the heap allocator return hash-for-home pages by default? */

extern int hash_default;

arch/tile/include/asm/signal.h

+4 −0
Original line number Diff line number Diff line
@@ -28,6 +28,10 @@ struct pt_regs; 
int restore_sigcontext(struct pt_regs *, struct sigcontext __user *);

int setup_sigcontext(struct sigcontext __user *, struct pt_regs *);

void do_signal(struct pt_regs *regs);

void signal_fault(const char *type, struct pt_regs *,

		  void __user *frame, int sig);

void trace_unhandled_signal(const char *type, struct pt_regs *regs,

			    unsigned long address, int signo);

#endif



#endif /* _ASM_TILE_SIGNAL_H */

arch/tile/kernel/compat_signal.c

+2 −2
Original line number Diff line number Diff line
@@ -317,7 +317,7 @@ long compat_sys_rt_sigreturn(struct pt_regs *regs) 
	return 0;



badframe:

	force_sig(SIGSEGV, current);

	signal_fault("bad sigreturn frame", regs, frame, 0);

	return 0;

}
@@ -431,6 +431,6 @@ int compat_setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info, 
	return 0;



give_sigsegv:

	force_sigsegv(sig, current);

	signal_fault("bad setup frame", regs, frame, sig);

	return -EFAULT;

}

arch/tile/kernel/signal.c

+124 −4
Original line number Diff line number Diff line
@@ -39,7 +39,6 @@ 


#define _BLOCKABLE (~(sigmask(SIGKILL) | sigmask(SIGSTOP)))





SYSCALL_DEFINE3(sigaltstack, const stack_t __user *, uss,

		stack_t __user *, uoss, struct pt_regs *, regs)

{
@@ -78,6 +77,13 @@ int restore_sigcontext(struct pt_regs *regs, 
	return err;

}



void signal_fault(const char *type, struct pt_regs *regs,

		  void __user *frame, int sig)

{

	trace_unhandled_signal(type, regs, (unsigned long)frame, SIGSEGV);

	force_sigsegv(sig, current);

}



/* The assembly shim for this function arranges to ignore the return value. */

SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs)

{
@@ -105,7 +111,7 @@ SYSCALL_DEFINE1(rt_sigreturn, struct pt_regs *, regs) 
	return 0;



badframe:

	force_sig(SIGSEGV, current);

	signal_fault("bad sigreturn frame", regs, frame, 0);

	return 0;

}
@@ -231,7 +237,7 @@ static int setup_rt_frame(int sig, struct k_sigaction *ka, siginfo_t *info, 
	return 0;



give_sigsegv:

	force_sigsegv(sig, current);

	signal_fault("bad setup frame", regs, frame, sig);

	return -EFAULT;

}
@@ -245,7 +251,6 @@ static int handle_signal(unsigned long sig, siginfo_t *info, 
{

	int ret;





	/* Are we from a system call? */

	if (regs->faultnum == INT_SWINT_1) {

		/* If so, check system call restarting.. */
@@ -363,3 +368,118 @@ done: 
	/* Avoid double syscall restart if there are nested signals. */

	regs->faultnum = INT_SWINT_1_SIGRETURN;

}



int show_unhandled_signals = 1;



static int __init crashinfo(char *str)

{

	unsigned long val;

	const char *word;



	if (*str == '\0')

		val = 2;

	else if (*str != '=' || strict_strtoul(++str, 0, &val) != 0)

		return 0;

	show_unhandled_signals = val;

	switch (show_unhandled_signals) {

	case 0:

		word = "No";

		break;

	case 1:

		word = "One-line";

		break;

	default:

		word = "Detailed";

		break;

	}

	pr_info("%s crash reports will be generated on the console\n", word);

	return 1;

}

__setup("crashinfo", crashinfo);



static void dump_mem(void __user *address)

{

	void __user *addr;

	enum { region_size = 256, bytes_per_line = 16 };

	int i, j, k;

	int found_readable_mem = 0;



	pr_err("\n");

	if (!access_ok(VERIFY_READ, address, 1)) {

		pr_err("Not dumping at address 0x%lx (kernel address)\n",

		       (unsigned long)address);

		return;

	}



	addr = (void __user *)

		(((unsigned long)address & -bytes_per_line) - region_size/2);

	if (addr > address)

		addr = NULL;

	for (i = 0; i < region_size;

	     addr += bytes_per_line, i += bytes_per_line) {

		unsigned char buf[bytes_per_line];

		char line[100];

		if (copy_from_user(buf, addr, bytes_per_line))

			continue;

		if (!found_readable_mem) {

			pr_err("Dumping memory around address 0x%lx:\n",

			       (unsigned long)address);

			found_readable_mem = 1;

		}

		j = sprintf(line, REGFMT":", (unsigned long)addr);

		for (k = 0; k < bytes_per_line; ++k)

			j += sprintf(&line[j], " %02x", buf[k]);

		pr_err("%s\n", line);

	}

	if (!found_readable_mem)

		pr_err("No readable memory around address 0x%lx\n",

		       (unsigned long)address);

}



void trace_unhandled_signal(const char *type, struct pt_regs *regs,

			    unsigned long address, int sig)

{

	struct task_struct *tsk = current;



	if (show_unhandled_signals == 0)

		return;



	/* If the signal is handled, don't show it here. */

	if (!is_global_init(tsk)) {

		void __user *handler =

			tsk->sighand->action[sig-1].sa.sa_handler;

		if (handler != SIG_IGN && handler != SIG_DFL)

			return;

	}



	/* Rate-limit the one-line output, not the detailed output. */

	if (show_unhandled_signals <= 1 && !printk_ratelimit())

		return;



	printk("%s%s[%d]: %s at %lx pc "REGFMT" signal %d",

	       task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,

	       tsk->comm, task_pid_nr(tsk), type, address, regs->pc, sig);



	print_vma_addr(KERN_CONT " in ", regs->pc);



	printk(KERN_CONT "\n");



	if (show_unhandled_signals > 1) {

		switch (sig) {

		case SIGILL:

		case SIGFPE:

		case SIGSEGV:

		case SIGBUS:

			pr_err("User crash: signal %d,"

			       " trap %ld, address 0x%lx\n",

			       sig, regs->faultnum, address);

			show_regs(regs);

			dump_mem((void __user *)address);

			break;

		default:

			pr_err("User crash: signal %d, trap %ld\n",

			       sig, regs->faultnum);

			break;

		}

	}

}

arch/tile/kernel/single_step.c

+4 −0
Original line number Diff line number Diff line
@@ -186,6 +186,8 @@ static tile_bundle_bits rewrite_load_store_unaligned( 
			.si_code = SEGV_MAPERR,

			.si_addr = addr

		};

		trace_unhandled_signal("segfault", regs,

				       (unsigned long)addr, SIGSEGV);

		force_sig_info(info.si_signo, &info, current);

		return (tile_bundle_bits) 0;

	}
@@ -196,6 +198,8 @@ static tile_bundle_bits rewrite_load_store_unaligned( 
			.si_code = BUS_ADRALN,

			.si_addr = addr

		};

		trace_unhandled_signal("unaligned trap", regs,

				       (unsigned long)addr, SIGBUS);

		force_sig_info(info.si_signo, &info, current);

		return (tile_bundle_bits) 0;

	}